https://www.cbr.com/tv-cameos-make-no-sense/

Sometimes, even the most beloved TV shows force blatantly out-of-place celebrity cameos.

Some that come to mind:

Full House - on occasion in several episodes the musical group The Beach Boys would pop up every once in awhile for no apparent reason, considering that small kids were the target audience they wouldn't know who they were. (John Stamos was friends with them in real life and appeared in the Kokomo music video)

Mr. Belvedere - Bob Uecker in real life was a former baseball player and sports announcer yet in some instances out of the blue we'd get Robert Goulet of all people to cameo in some episodes.